Mekongbathynella kampucheana, Park, 2021

Park, Jong-Geun, 2021, Four new species of Parabathynellidae (Bathynellacea, Syncarida) from the interstitial environment of the Mekong River, Journal of Natural History 55 (17 - 18), pp. 1075-1111 : 1077-1084

publication ID	https://doi.org/ 10.1080/00222933.2021.1936677
persistent identifier	https://treatment.plazi.org/id/1131F815-E96A-FFB2-A04B-FB956499C01E
treatment provided by	Plazi
scientific name	Mekongbathynella kampucheana
status	sp. nov.

Treatment

Mekongbathynella kampucheana sp. n. ( Figures 1–5 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 )

Etymology

The specific epithet is derived from the old name of Cambodia, Kampuchea. Gender feminine.

Type material

Holotype. Adult female, dissected on six slides. Cambodia, Stung Treng Province, Siem Bok District, Stung treng Town , Interstitial in sand bank of Mekong River , depth 30 cm, 10 m from shore, site 24 (13°32’26.5”N, 106°00’23.2”E), 27. April 2012 (Collector: J.-L. Cho) ( NIBR IV0000266926 View Materials ). GoogleMaps

Allotype. Adult male dissected on six slides, same data as holotype ( NIBR IV0000266927 View Materials ). GoogleMaps

Paratypes. One adult female dissected on five slides, same data as holotype ( NIBR IV0000266928 View Materials ), one adult male dissected on six slides ( NIBR IV0000266929 View Materials ), seven females and five males each kept as a whole specimen on separate slides ( NIBR IV0000266930 View Materials – IV0000266941 View Materials ) GoogleMaps .

Description of adult female (holotype)

Body. Length 1.21 mm (average of other females: 1.21, n = 8), approximately 12 times as long as wide. Head somewhat shorter than anterior three thoracic segments combined ( Figure 1 View Figure 1 (a)).

Antennule ( Figure 1 View Figure 1 (b)) 6-segmented. First segment with one seta on inner distal margin, with one simple dorsal seta, and one dorsal, two lateral plumose setae. Second segment with one group of four plumose setae and one simple setae on inner distal margin. Third segment with two lateral setae (inner one tiny) and one inner ventral seta. Inner flagellum with three simple setae. Fourth segment with one stub seta and one plumose seta on dorsal margin, and two plumose setae on outer distal apophysis. Fifth segment with three setae on inner margin, with three aesthetascs and one simple seta dorsally. Sixth segment with three subterminal aesthetascs and four simple setae.

Antenna ( Figure 1 View Figure 1 (f)) 6-segmented, as long as antennular segments 1–4. Setal formula: 0 + 0/0 + 0/1 + 0/1 + 1/0 + 0/4(1).

Labrum ( Figure 1 View Figure 1 (g)) flat with eight median teeth flanked by one bulge carrying two spinules on both sides. Inner surface with one tiny median protuberance surrounded by six rows of spinules, one pair of teats, two pairs of spinules on the external distal section, and 10 oblique rows of spinules in the medio-proximal section.

Mandible ( Figure 2 View Figure 2 (a, b)) with incisor process of four teeth. Tooth of ventral edge long and seta-like. Spine row consisting of six serrated spines. Palp one-segmented and three times longer than wide, with one apical seta exceeding incisor process in length.

Maxillule ( Figure 2 View Figure 2 (c)) 2-segmented. Proximal segment with four claw-like setae on inner distal margin. Distal segment distally with two smooth spines, three spines and one flat round proximal projection carrying tiny spinules on inner margin, and with three simple setae on outer distal margin. Two distal spines on inner margin serrated, proximal spine smooth.

Maxilla ( Figure 2 View Figure 2 (d)) 4-segmented, setal formula 1-3-8-6. Second segment without medial seta. Most distal seta of third segment claw-like, as large as claw-like seta of fourth segment.

Thoracopods I–VII ( Figures 2 View Figure 2 (e, f, g), 3(a, b, c), and 4(a)). Thoracopods I–IV increasing in size posteriorly. Thoracopods IV–VII similar in size. Thoracopods III–VII each bearing one epipod on protopod. Protopod of thoracopod VI with protruded inner margin. Thoracopods I–VII each with one basipodal seta. Exopod two-segmented throughout. Ventral seta of proximal segment not shorter than distal segment, dorsal seta tiny. Dorsal seta of distal segment shorter than basis of ventral seta. Endopod four-segmented, setal formulae: Th I: 1 + 0/0 + 1/1 + 0/3(1); Th II–VII: 0 + 0/0 + 1/0 + 0/3(1).

Thoracopod VIII ( Figure 4 View Figure 4 (b, c)) in form of flat and round projection being basally fused.

First pleopod absent.

Uropod ( Figure 5 View Figure 5 (a, c)) with two subterminal spines of equal size in slightly oblique row on inner margin of sympod. Endopod 48% as long as sympod, with one distal spine, with two dorsal plumose setae, and two terminal setae. Distal outer margin protruded prominently. Exopod as long as endopod, with one basi-ventral seta and three setae on outer and terminal margin.

Pleotelson ( Figure 5 View Figure 5 (b, c)) with one lateral seta near the base of furcal rami on both sides.

Anal operculum ( Figure 5 View Figure 5 (b, c)) protruded with round margin nearly reaching the distal end of furcal rami.

Furcal rami ( Figure 5 View Figure 5 (b, c)) 1.2 times as long as wide, with two large distal spines and one smaller spine on inner margin and one simple seta and one plumose setae dorsally.

Description of adult male (allotype)

Body ( Figure 1 View Figure 1 (a)). length 1.20 mm (average of other males: 1.00, n = 6). Differing from the female in second antennular segment, flat inner margin of thoracopod VI and thoracopod VIII, and body length.

Second antennular segment ( Figure 1 View Figure 1 (c, d, e)) with a two-lobed protrusion on the ventro-distal side, with of similar thickness. Other setal ornamentation similar to second antennular segment of female.

Thoracopod VIII ( Figure 4 View Figure 4 (d, e)) massive in relation to body size, as long as 8th thoracomer, 1.3 times longer than wide in lateral view. Protopod predominant on anterior part, massive and globular in lateral view; penial region prominent, exceeding height of exopod in lateral view, with dentate lobe carrying 16 dentils. Epipod flat and round. Basipod inserted behind penial lobe, almost same size of protopod in lateral view, main axis parallel to that of 8th thoracomere, without setae, middle part of inner margin of basipod forming two smooth lobes directed towards the endopod. Exopod as large as half size of basipod, semicircular in general form, inserted widely along the basipod; distal margin with one smooth lobe, one lobe carrying three distal setae and one medial seta and one group of three distally serrated teeth on bulge. Endopod pointing backwards, as long as one fifth of basipod, with two terminal setae.